Eosinophilia in Pulmonary Practice

Eosinophilia is a frequently encountered laboratory abnormality in pulmonary practice and is associated with a wide spectrum of respiratory diseases ranging from benign allergic conditions to severe systemic disorders. Eosinophils play a key role in host defense, particularly in parasitic infections, but are also central to the pathogenesis of various inflammatory and hypersensitivity lung diseases. The presence of eosinophilia in patients with respiratory symptoms often presents a diagnostic challenge due to the diversity of underlying etiologies and overlapping clinical features. The objective of this study was to review the causes, pathophysiology, clinical spectrum, diagnostic approach, and management of eosinophilia in pulmonary practice. A narrative review was conducted using literature from PubMed, Scopus, and Google Scholar. Relevant articles published in English were identified using keywords such as "eosinophilia," "pulmonary eosinophilia," "eosinophilic lung diseases," "asthma," and "hypereosinophilic syndrome." Original research studies, clinical guidelines, and review articles focusing on respiratory manifestations of eosinophilia were included in the study. Articles lacking clinical relevance or focusing exclusively on nonpulmonary conditions were excluded from the study. The selected literature was synthesized qualitatively to highlight key clinical and diagnostic aspects. Eosinophilia in pulmonary practice may result from a variety of conditions, including allergic diseases such as asthma and allergic bronchopulmonary aspergillosis, parasitic infections, drug reactions, autoimmune disorders, and primary eosinophilic lung diseases such as acute and chronic eosinophilic pneumonia. Clinical presentation varies widely, ranging from mild respiratory symptoms to severe hypoxemic respiratory failure. Peripheral blood eosinophilia, along with radiological findings and bronchoalveolar lavage analysis, plays a crucial role in diagnosis. A systematic approach is essential to differentiate between primary and secondary causes. Management strategies depend on the underlying etiology and often include corticosteroids, antiparasitic therapy, or targeted biologic agents in selected conditions. Eosinophilia represents an important diagnostic clue in respiratory medicine and requires a structured and comprehensive evaluation. Early identification of the underlying cause is essential for appropriate management and prevention of complications. Advances in understanding eosinophil biology and targeted therapies are likely to improve outcomes in eosinophilic lung diseases.